In the following, a case in which date calendar information is displayed in a timepiece in larger numbers, using a timepiece calendar device as an example of a display device, is described.
Conventionally, for large display of a calendar in a calendar window, two date dials are used to display the calendar such that the calendar letters on the respective date dials are shown in the calendar window defined on the dial. Specifically, an arrangement in which one of the two date dials is advanced while the other is kept still and, thereafter, the other is advanced while the one is kept still makes it possible to display the letters on the two date dials. This is disclosed in Swiss Patent No. CH 660941 B5 (see FIGS. 1 and 3).
This concept is disclosed also in Japanese Patent Laid-Open Publications Nos. 2005-156562 (FIGS. 4, 5, and 6) and 2005-156563 (FIGS. 2, 3, and 4), both disclosed later than the priority date of this application.
The above-described three patent documents are common in that the upper date dial of the two date dials has sixteen sectors, while the lower date dial has seventeen sectors. Accordingly, the upper and lower date dials have different numbers of teeth in the toothed portion, with the upper date dial having sixteen teeth and the lower date dial having seventeen teeth. The difference of one tooth results in a difference (displacement) in positional relationship in a plan view between the teeth of the upper and lower date dials.
Thus, as disclosed in Swiss Patent No. CH 660941 B5 (FIG. 1), Japanese Patent Laid-Open Publication Nos. 2005-156562 (FIG. 7) and 2005-156563 (FIG. 5), both disclosed later than the priority date of this application, two date jumpers in two shapes mounted in different positions in a plan view are necessary, one shape for the upper date dial and the other shape for the lower date dial. This results in the need for a wider space and a complicated structure.
When a position where one tooth of the upper date dial overlaps in a plan view one tooth of the lower date dial is reserved for a drive wheel, a space for mounting a date corrector setting wheel cannot be ensured as no other such space where the tooth of the upper date dial overlaps the tooth of the lower date dial is available. Thus, initial CH 660941 B5 (FIG. 1) and Japanese Patent Laid-Open Publication No. 2005-156563 (FIG. 6), disclosed later than the priority date of the present application, make a proposal without a date correction mechanism. However, as a date correction mechanism is necessary to advance the date dial for date matching when the timepiece date becomes different from the current date at the end of a short month, at activation of the timepiece, or due to battery exchange, a proposal including no date correction mechanism is inconvenient as it makes a correction operation troublesome. Therefore, Japanese Patent Laid-Open Publication No. 2005-156562 (FIG. 8) discloses a two-toothed portion structure in which a toothed portion having different positions (pitches) is placed on the toothed portion of the lower date dial, the toothed portion to place. This results in the lower date dial having a complicated structure.
An object of the present invention is to propose a display device and a timepiece calendar display capable of large display of information and solving a conventional technical problem.